The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Some embodiments relate to methods applied to a well bore penetrating a subterranean formation.
Hydrocarbons (oil, condensate, and gas) are typically produced from wells that are drilled into the formations containing them. For a variety of reasons, such as inherently low permeability of the reservoirs or damage to the formation caused by drilling and completion of the well, the flow of hydrocarbons into the well is undesirably low. In this case, the well is “stimulated” for example using hydraulic fracturing, chemical (usually acid) stimulation, or a combination of the two (called acid fracturing or fracture acidizing).
Hydraulic fracturing of horizontal wells as well as multi-layered formations frequently requires using diverting techniques in order to enable fracturing redirection between different zones. The list of these diverting methods includes, but not limited to, using mechanical isolation devises such as packers and well bore plugs, setting bridge plugs, pumping ball sealers, pumping slurred benzoic acid flakes and removable/degradable particulates. As well, other treatment may require use of diverting techniques.
Acid fracturing is a widely used technique for increasing the production of oil from a well that penetrates an underground limestone or dolomite hydrocarbon bearing formation. Typically during an acid fracturing treatment, a pad fluid is rapidly injected into the formation so as to create a buildup in wellbore pressure sufficient to overcome compressive stresses and tensile strength of the rock formation. When subjected to a sufficient pressure, the rock fails allowing a crack, also referred to as a fracture, to form in the formation. Continued fluid injection often increases the fracture's length, height and width. Acid is then injected into the fracture and the acid chemically reacts with the face of the fracture. The reaction of the acid with face of the fracture etches the face so that when the fracture closes flow channels are created that extend deep into the formation. If the acid fracturing treatment is properly done, these flow channels remain open when the well is placed back on production, thus increasing the productive capacity of the well.
Limitations in the use of acid fracturing is largely due to, at least:                The total leakoff of the acid during the treatment keeps on increasing as the fracture propagates and as the walls of the fracture get partially dissolved; as a result it is difficult to maintain a treatment pressure high enough to keep on propagating the fracture and etching the fracture along its length. In the end, a fracture shorter than optimum is generated;        The stress to which the formation is subject to, tends to close the fracture and generate pinch points. Those pinch points are very detrimental to the production of the well, particularly when they are close to the wellbore. Therefore it is desirable to maximize the amount of etching in the near wellbore region, so that fracture walls remain apart when the fracture eventually closes.        
The industry would welcome methods to address the previously mentioned limitations.